Headrest for vehicles

ABSTRACT

Disclosed herein is a headrest for vehicles, which can fixedly support the passenger&#39;s head including the mandible in an automobile crash, thereby preventing hyper-flexion of the neck. The headrest comprises a pair of support rods fitted at the top of a backrest of an automotive vehicle seat, first and second cushion units rotatably fitted at the top of the respective support rods, respectively, at least one elastic member for elastically connecting the first and second cushion units, jaw-restraint portions formed at opposite sides of the first and second cushion units, respectively, and stoppers for keeping the support rods in an immobilized state after the first and second cushion units are rotated to a predetermined degree. By using the headrest of the present invention, it is possible to minimize injury to the neck of the passenger. Especially, the present invention can effectively protect the passenger&#39;s neck, which is further endangered when the passenger wears a safety belt, and thus can secure the greatest safety of the passenger.

BACKGROUND OF THE INVENTION

1Field of the Invention

The present invention relates to a headrest for vehicles, and moreparticularly to a headrest for vehicles, which can fixedly support thepassenger's head including the mandible in an automobile crash, therebypreventing sprain due to hyper-flexion of the neck.

2. Description of the Related Art

In general, an automotive vehicle seat is provided at the top of abackrest with a headrest for supporting the passenger's occiput. Such aheadrest serves to relieve shock applied to the occiput in an automobilecrash, thereby minimizing injury to the passenger.

However, since headrests are designed to only to support the passenger'socciput, they have a problem in that they cannot provide protection tothe neck, in spite of the fact that the neck is an extremely fragileregion of the human body, in an automobile crash.

In an automobile crash, such as a broadside, a head-on or rear-endcollision, passengers are mostly injured at their neck. The followingtable represents percentages of injured passengers according to bodyregions. As can be seen from the table, in years 1998 and 2000, thepercentage of passengers, which suffered neck injuries, is the highest,and waist and head injuries follow in order. Year 1998 Year 2000 NoteNeck (%) 62.3% 69.9% 7.3% increase Waist (%) 33.7% 32.9% 0.8% reduceHead (%) 31.0% 28.0%   3% reduce

In order to solve the above problem, there have been conventionallydeveloped neck protecting devices, which are designed to elasticallysupport the scruff of the passenger's neck so as to absorb shockgenerated in an automobile crash. One example of the conventional neckprotecting devices is shown in FIGS. 9 a and 9 b, which are,respectively, a plan view and a side view. The device shown is disclosedin Korean Registration Patent Publication No. 302153, titled in“AUXILIARY SUPPORT DEVICE OF HEADREST FOR VEHICLES”.

Referring to FIGS. 9 a and 9 b, a headrest 200, installed at the top ofa backrest 101 of a conventional automotive vehicle seat 100, comprisesa pair of support rods 220 fitted at the top of the backrest 101, and ahead cushion 210 fitted at the top of the support rods 220 forsupporting the passenger's occipital bone.

Between the head cushion 210 and the backrest 101 an auxiliary supportdevice 300 is provided for supporting the scruff of the neck. Theauxiliary support device 300 comprises an air bag 310, and a pluralityof springs 320 for elastically supporting the rear surface of the airbag 310.

Although the above described conventional headrest, provided with theauxiliary support device, can relieve shock generated at the moment ofan automobile crash by supporting the passenger's occiput as well as thescruff of the neck at the rear side thereof, it cannot preventhyperflexion of the neck caused as the passenger's head reboundsforward, thereby potentially causing sprain to the passenger' neck. Nowexplanation is made in detail to such sprain to the neck according tokinds of traffic accidents.

First, in case of a sudden acceleration or rear-end collision of anautomotive vehicle, the body of the passenger is moved forward alongwith the vehicle, but the passenger's head is pushed rearward due toinertia. This results in a successive hyperextension-hyperflexioninjury, and consequently sprains the neck. Even in case of a sudden stopor head-on collision of an automotive vehicle in motion, the passenger'shead is pushed forward by inertia as the vehicle is momentarily stopped.This similarly results in a successive hyperflexion-hyperextensioninjury, and consequently sprains the neck.

Such sprain is caused due to the fact that the passenger's head is notstably immobilized so as not to move in an automobile crash. When thepassenger wears a safety belt and thus his/her body is stablyimmobilized, especially, a larger moment is applied to the passenger'sneck, resulting in a risk of whiplash due to hyperflexion. Such a riskhas awakened us to the urgent need for appropriate measures to safeguardpassengers.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the aboveproblems, and it is an object of the present invention to provide aheadrest for vehicles, which can fixedly support the passenger's headincluding the mandible in an automobile crash, thereby preventing spraindue to hyperflexion of the neck.

It is another object of the present invention to provide a headrest forvehicles, which is designed to closely support the passenger's occipitalbone, thereby allowing shock applied to the occipital bone in anautomobile crash to be rapidly distributed, and allowing lessen load ofthe passenger's head to be transmitted to the backbone.

It is a further object of the present invention to provide a headrestfor vehicles, which can automatically immobilize the passenger's head inan automobile crash, such as a broadside, head-on or rear-end collision.

It is yet another object of the present invention to provide a headrestfor vehicles, which automatically keeps a constant distance relative tothe passenger's head according to the position of the head, and thusenables rapid and accurate support of the passenger's head in anautomobile crash.

In accordance with one aspect the present invention, the above and otherobjects can be accomplished by the provision of a headrest for a vehiclecomprising: a pair of support rods fitted at the top of a backrest of anautomotive vehicle seat; first and second cushion units rotatably fittedat the top of the respective support rods, respectively; at least oneelastic member for elastically connecting the first and second cushionunits; jaw-restraint portions formed at opposite sides of the first andsecond cushion units, respectively; and stoppers for keeping the supportrods in an immobilized state after the first and second cushion unitsare rotated to a predetermined degree.

Preferably, the first and second cushion units include: a pair ofsymmetrical seating portions, respectively, formed at positionscorresponding to the passenger's occipital bone; and a pair of auxiliarycushion members located below the respective seating portions forsupporting the bottom of the occipital bone.

In accordance with another aspect the present invention, the above andother objects can be accomplished by the provision of a headrest for avehicle comprising: first and second cushion units rotatably fitted atthe top of a pair of support rods, respectively, the support rods beingfitted at the top of a backrest of an automotive vehicle seat, the firstand second cushion units having jaw-restraint portions formed atopposite sides thereof, respectively; impact sensors for detecting shockapplied to the vehicle in an automobile crash, and outputting signals;pressure sensors for detecting shock caused as the passenger's headcollides against the first and second cushion units, and outputtingsignals; a control unit for receiving the signals from the impact sensorand the pressure sensors, and outputting a control signal for causingrotation of the first and second cushion units; driving units forrotating the first and second cushion units according to the controlsignal; and stoppers for keeping the first and second cushion units inan immobilized state after they are rotated by a predetermined degree.

In accordance with yet another aspect the present invention, the aboveand other objects can be accomplished by the provision of a headrest fora vehicle comprising: first and second cushion units rotatably fitted atthe top of a pair of support rods, respectively, the support rods beingfitted at the top of a backrest of an automotive vehicle seat, the firstand second cushion units having jaw-restraint portions formed atopposite sides thereof, respectively; impact sensors for detecting shockapplied to the vehicle in an automobile crash, and outputting signals; adistance adjustment unit for maintaining a constant distance between thepassenger's head and the first and second cushion units; a control unitfor receiving the signals from the impact sensor, and outputting acontrol signal for causing rotation of the first and second cushionunits; driving units for rotating the first and second cushion unitsaccording to the control signal; and stoppers for keeping the first andsecond cushion units in an immobilized state after they are rotated by apredetermined degree.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a perspective view illustrating an automotive vehicle seatprovided with a headrest in accordance with a first embodiment of thepresent invention;

FIGS. 2 a and 2 b are a front view and a plan view, respectively,illustrating the headrest shown in FIG. 1;

FIG. 3 is a plan view illustrating the operation of the headrest shownin FIG. 2 b;

FIG. 4 is a cross-sectional view illustrating a stopper shown in FIG. 2b;

FIG. 5 is a cross-sectional view illustrating another example of thestopper shown in FIG. 2 b;

FIG. 6 is a cross-sectional view illustrating a headrest in accordancewith a second embodiment of the present invention;

FIG. 7 is a front sectional view illustrating a driving unit for use inthe headrest shown in FIG. 6;

FIG. 8 is a side sectional view illustrating a headrest in accordancewith a third embodiment of the present invention; and

FIGS. 9 a and 9 b are a plan view and a side view, respectively,illustrating a headrest of the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in greater detail to preferred embodiments ofthe invention, examples of which are illustrated in the accompanyingdrawings.

FIG. 1 is a perspective view illustrating an automotive vehicle seatprovided with a headrest in accordance with a first embodiment of thepresent invention. FIGS. 2 a and 2 b are a front view and a plan view,respectively, illustrating the headrest shown in FIG. 1.

As shown in the above drawings, a headrest for vehicles in accordancewith a first embodiment of the present invention, which is designated asreference numeral 1, comprises: a pair of support rods 10 fitted at thetop of the backrest 101 of the automotive vehicle seat 100; first andsecond cushion units 20 a and 20 b rotatably installed at the top of therespective support rods 10; an elastic member 30 for elasticallyconnecting the first and second cushion units 20 a and 20 b; ajaw-restraint portions 21 a and 21 b formed at opposite sides of thefirst and second cushion units 20 a and 20 b, respectively; and a pairof stoppers 40 a and 40 b for stopping rotation of the first and secondcushion units 20 a and 20 b after they completely surround thepassenger's head.

Within the first and second cushion units 20 a and 20 b are disposedcylindrical sleeves 24 a and 24 b, respectively, for use in theinsertion of the respective support rods 10. These sleeves 24 a and 24 benable the first and second cushion units 20 a and 20 b to freely rotateabout the respective support rods 10.

The jaw-restraint portions 21 a and 21 b, formed at the opposite sidesof the first and second cushion units 20 a and 20 b, protrude forward sothat they can surround the passenger's head including the mandible asthe first and second cushion units 20 a and 20 b rotate about thesupport rods 10.

The stoppers 40 a and 40 b are disposed within the first and secondcushion units 20 a and 20 b. At the moment when the jaw-restraintportions 21 a and 21 b completely surround the passenger's head, thestoppers 40 a and 40 b serve to stop rotation of the first and secondcushion units 20 a and 20 b in order to immobilize the passenger's head.Detailed description related to the operation of the stoppers 40 a and40 b will follow with reference to FIG. 3.

Meanwhile, at front surfaces of the first and second cushion units 20 aand 20 b are symmetrically formed concave seating portions 22 a and 22b. These concave seating portions 22 a and 22 b are positioned incorrespondence to the passenger's occipital bone, so as to closelysupport the occipital bone, thereby serving to allowing shock applied tothe occipital bone in an automobile crash to be rapidly distributed andthus providing protection to the brain.

Attached at the front surfaces of the first and second cushion units 20a and 20 b below the concave seating portions 22 a and 22 b areauxiliary cushion members 23 a and 23 b for supporting the bottom of theoccipital bone. These auxiliary cushion members 23 a and 23 b serve tolessen load of the head to be transmitted to the backbone, resulting ina comfortable ride for the passenger.

Preferably, the auxiliary cushion members 23 a and 23 b are made ofmemory foam so that they come into close contact with the occipital boneregardless of different occipital bone's shapes in order to multiply thecomfort of the ride.

FIG. 3 is a plan view illustrating the operation of the headrest 1 shownin FIG. 2 b. FIG. 4 is a cross-sectional view illustrating the stopper40 b shown in FIG. 2 b.

As shown in FIGS. 3 and 4, when the occiput of the passenger is rapidlymoved back in an automobile crash, and collides against the first andsecond cushion units 20 a and 20 b, by collision shock applied thereto,the first and second cushion units 20 a and 20 b are rotated about thesupport rods 10 so as to surround the passenger's occiput.

Considering the configuration of the stoppers in relation to the secondcushion unit 20 b as shown in FIG. 4, the stopper 40 b comprises: a case41 provided inside the second cushion unit 20 b; the latch 42 protrudingat one end thereof out of the case 41 so as to come into contact withthe outer periphery of the support rod 10 within the second cushion unit20 b; the spring 43 disposed inside the case 41 so as to elasticallysupport the other end of the latch 42; the fixing groove 44 defined atthe outer periphery of the support rod 10 for allowing the latch 42 tobe lockably engaged therein as a result of rotation of the secondcushion unit 20 b; and a pulling member 45 for pulling out the latch 42inserted in the fixing groove 44.

Therefore, at the moment that the jaw-restraint portions 21 a and 21 bsurround the mandible as a result of rotation of the first and secondcushion units 20 a and 20 b, latches 42 formed at the stoppers 40 a and40 b are coincided with fixing grooves 44 defined at the outer peripheryof the respective support rods 10, and lockably engaged in the fixinggrooves 44 by the elasticity of springs 43, thereby allowing the firstand second cushion units 20 a and 20 b to be fixedly maintained at sucha rotated position.

Since the support rods 10 are surrounded by the sleeves 24 a and 24binside the first and second cushion units 20 a and 20 b, the sleeves 24a and 24 b have through-bores (not designated), respectively, forallowing the end of the respective latches 42 to come into contact withthe outer periphery of the respective support rods 10 therethrough.

With such a configuration as stated above, shock, which is generated inthe course of the collision of the passenger's head against the firstand second cushion units 20 a and 20 b, is exhausted largely by virtueof the elasticity of the elastic member 30, resulting in effectivereduction of the shock transmitted to the brain of the passenger.

Further, since the jaw-restraint portions 21 a and 21 b are immobilizedin a state that they completely surround the passenger's head includingthe mandible, thereby serving to effectively restrict further movementof the head, sprain due to hyperflexion of the neck can be completelyprevented.

After the automobile crash, with reference to FIG. 4, the latches 42 areremoved from the fixing grooves 44 by means of the pulling members 45,thereby serving to release an immobilized state of the first and secondcushion units 20 a and 20 b. Each of the pulling members 45 has a wire450, which is connected at one end thereof to the other end of thecorresponding latch 42. The other end of the wire 450 protrudes out ofthe cushion unit. The pulling member 45 further has a pull grip 451provided at the outwardly-protruded end of the wire 450.

As both the pull grips 451 are simultaneously pulled, the latches 42 aredrawn from the fixing grooves 44 by means of the wires 450, therebyallowing the first and second cushion units 20 a and 20 b to be releasedfrom their immobilized state. The released first and second cushionunits 20 a and 20 b are automatically returned to their originalpositions by the elasticity of the elastic member 30.

FIG. 5 is a cross-sectional view illustrating another example of thestopper shown in FIG. 2 b. The shown example is different from the aboveembodiment in that springs 43′, used to elastically support the otherend of the respective latches 42 are plate springs rather than coilsprings.

FIG. 6 is a cross-sectional view illustrating a headrest in accordancewith a second embodiment of the present invention. FIG. 7 is a frontsectional view illustrating a driving unit for use in the headrest shownin FIG. 6.

In an automobile crash, signals from impact sensors (not shown) mountedin an automotive vehicle are inputted into a control unit (not shown).In succession, as the passenger's occiput is rapidly moved back due tosuch an automobile crash, and collides against the first and secondcushion units 20 a and 20 b, pressure sensors (not shown) disposedinside the first and second cushion units 20 a and 20 b detect shockapplied thereto by the passenger's head, thereby sending signals to thecontrol unit. Upon receiving the above described signals, the controlunit outputs a control signal to driving units, so that the first andsecond cushion units 20 a and 20 b, and the sleeves 24 a and 24 bdisposed therein are rotated about the support rods 10 according to theoperation of the driving units. In this way, the first and secondcushion units 20 a and 20 b are adapted to surround the passenger'shead.

The second embodiment employs a pair of stoppers, which are differentfrom those of the first embodiment. Considering now the configuration ofthe stoppers with reference to FIG. 6, the stopper comprises: a firstdetector 46 positioned just inside the outer periphery of the supportrod 10; a second detector 47 positioned just inside the inner peripheryof the sleeve 24 b, which surrounds the support rod 10, so as tocorrespond to the first detector 46; and a locking member 48 adapted tosupport the lateral surface of the support rod 10 when positions of thefirst and second detectors 46 and 47 coincide with each other as aresult of rotation of the second cushion unit 20 b, thereby serving tostop rotation of the second cushion unit 20 b and maintaining it in animmobilized state. It will be noted that the above configuration is alsoapplicable to the stopper of the first cushion unit 20 a.

Considering the locking members 48 of the stoppers in more detail, theyserve to immobilize the first and second cushion units 20 a and 20 b bymaking use of a frictional force. Each of the locking members 48comprises: a hydraulic or pneumatic cylinder 480; a clamp 481 whichcomes into close contact with the support rod 10 under operation of thecylinder 480 so as to generate a frictional force; and the control unit(not shown) for receiving a signal generated when positions of the firstand second detectors 46 and 47 coincide with each other, and sending adriving signal to the cylinder 480.

At the moment when the jaw-restraint portions 21 a and 21 b surround thepassenger's head including the mandible as a result of rotation of thefirst and second cushion units 20 a and 20 b, positions of the first andsecond detectors 46 and 47 coincide with each other, and thus theresultant signal is sent to the control unit. Thereby, the control unitdrives the cylinder 480 so that the clamp 481 compresses the lateralsurface of the support rod 10, thereby generating a frictional force forimmobilizing the first and second cushion units 20 a and 20 b.

In order to release such an immobilized state of the first and secondcushion units 20 a and 20 b, the cylinder 480 must be driven so as toremove a pressure applied to the clamp 481. Such a pressure removaloperation can be easily achieved by installing a separate operator unit(not shown) for inputting a release signal to the control unit.

Referring to FIG. 7 illustrating one of the driving units adapted to bedriven by a control signal from the control unit, in relation with thesecond cushion unit 20 b, the driving unit, designated as referencenumeral 50, has a servo-motor 51 fixed inside the second cushion unit 20b, and a power-transmission member 52 for transmitting a rotating forceof the servo-motor 51 to the support rod 10 inside the second cushionunit 20 b.

The power-transmission member 52 transmits the rotating force of theservo-motor 51 to the second cushion unit 20 b, thereby allowing thesecond cushion unit 20 b to rotate about the support rod 10. Such apower-transmission member 52 consists of a driving gear (not designated)provided at the servo-motor 51, and a driven gear (not designated)fitted around the support rod 10 so as to engage with the driving gear.

With such a configuration, if the impact sensors detect an automobilecrash, and successively, the pressure sensors inside the first andsecond cushion units 20 a and 20 b detect shock generated when thepassenger's head collides against the first and second cushion units 20a and 20 b, the control unit drives the servo-motor 51 so as to rotatethe driving gear. As the driving gears rotate around the driven gearsfitted to the respective support rods 10, the first and second cushionunits 20 a and 20 b are automatically rotated so as to fixedly supportthe passenger's head.

In this case, in order to allow the first and second cushion units 20 aand 20 b to be rapidly rotated, and be stopped in a state wherein theyfixedly support the passenger's head, data related to the rotating speedof the servo-motors 51 is inputted to the control unit.

Alternatively, a time required for the backward movement of thepassenger's head by inertia in an automobile crash may be previouslycalculated and stored in the control unit. Thereby, after the controlunit detects an automobile crash, the first and second cushion units 20a and 20 b are rotated by a predetermined time interval depending on thestored data.

FIG. 8 is a side sectional view illustrating a headrest in accordancewith a third embodiment of the present invention. The present embodimentemploys a distance adjustment unit for allowing the first and secondcushion units 20 a and 20 b at the top of the backrest 101 to be equallymoved toward the passenger's head according to the position of the head.By such a distance adjustment unit, therefore, the first and secondcushion units 20 a and 20 b can closely support the passenger's head.

Some passengers prefer to lean their head on the headrest, whereasothers prefer to space their head from the headrest. In the latter case,when a broadside collision occurs, the passenger's head is moved onlylaterally without colliding with the headrest. This makes it impossibleto obtain any protection by the headrest.

In order to solve the above problem, the present embodiment enables thefirst and second cushion units 20 a and 20 b to be closely spaced fromthe passenger's head, thereby allowing the first and second cushionunits 20 a and 20 b to freely rotate regardless of the collisiondirection of an automotive vehicle. This secures accurate and stablesupporting of the passenger's head.

The distance adjustment unit comprises: a distance sensor (S) fordetecting a distance between the passenger's occipital bone and thefirst and second cushion units 20 a and 20 b, and outputting acorresponding signal; the control unit for detecting the signal from thesensor (S), and outputting a control signal if the detected distanceexceeds a predetermined value; and a position adjustor 60 for adjustingpositions of the first and second cushion units 20 a and 20 b accordingto the control signal. The distance sensor (S) is selected from amongconventional photo-sensors, ultrasonic sensors, etc. Such a distancesensor (S) is installed between the support rods 10, and is adapted tomeasure the distance between the occiput or neck of the passenger andthe support rods 10, thereby allowing the distance to be kept in aconstant value.

In the present embodiment, as can be seen from FIG. 8, such a distanceadjustment is achieved by adjusting an inclination angle of the firstand second cushion units 20 a and 20 b. For this, the support rods 10are hingedly fixed at their lower ends inside the backrest 101, and theposition adjustor 60, which is also fixed inside the backrest 101,serves to allow the first and second cushion units 20 a and 20 b to bepivotably rotated by a desired angle. As the position adjustor 60 isused a conventional cylinder.

In a state wherein a desired distance value between the first and secondcushion units and the passenger's head is previously set in the controlunit, only when the distance value detected by the distance sensor (S)exceeds the desired preset value, the control unit is adapted to outputa control signal to the position adjustor 60.

As stated above in relation with FIG. 7, the first and second cushionunits 20 a and 20 b are pivotably rotated in an automobile crash so asto fixedly support the passenger's head. In this case, the first andsecond cushion units 20 a and 20 b are automatically pivotedcorresponding to the position of the passenger's occipital bone, therebykeeping a constant distance relative to the passenger's head. Thisenables rapid and accurate support of the passenger's head even if thehead is moved laterally in case of a broadside collision.

Meanwhile, the present embodiment employs a separate manually-operatedswitch provided at an automotive vehicle for selectively operating thedistance adjustment unit as occasion demands by controlling a powersource of the distance adjustment unit. Further, in order to allowpositions of the first and second cushion units to be selectivelyadjusted by the distance adjustment unit only when a passenger rides inthe vehicle, the vehicle is provided with a seat sensor for detectingthe presence of the passenger on the vehicle seat.

In this case, through the use of the switch for turning on/off the powersource of the distance adjustment unit according to a signal from theseat sensor, the first and second cushion units are automaticallypivoted in boarding, or automatically stopped in alighting.

The seat sensor serves to confirm the presence of the passenger, and isselectable from among various types of sensors, for example,pressure-sensitive sensors, which are usually installed on a vehicleseat for detecting the weight of the passenger, and sensors, which areusually installed in the vehicle for detecting ignition of the vehicle.

As apparent from the above description, the present invention provides aheadrest for vehicles, which can fixedly support the passenger's headincluding the mandible in an automobile crash, thereby preventing spraindue to hyperflexion of the neck. This has an effect of minimizing injuryto the neck of the passenger. Especially, in spite of the fact that thepassenger's neck is further endangered when the passenger wears a safetybelt, the headrest of the present invention can effectively protect thepassenger's neck, and can secure the greatest safety of the passenger.

Further, by forming seating portions at first and second cushion unitsof the headrest for closely supporting the passenger's occiput, shockapplied to the occiput in an automobile crash can be rapidlydistributed, resulting in minimization in transmission of the shock tothe brain.

In addition to the seating portions, by providing auxiliary cushionmembers therebelow for supporting the bottom of the occiput, it ispossible to allow lessen load of the passenger's head to be transmittedto the backbone, resulting in a more comfortable ride.

According to the present invention, the first and second cushion unitsmay be adapted to automatically support the passenger's head in anautomobile crash. This enables more rapid and accurate support of thehead and thus results in more successful lifesaving.

Furthermore, according to the present invention, since the first andsecond cushion units are adapted to automatically keep a constantdistance relative to the passenger's head according to position of thehead, and thus rapidly support the head, it is possible to protect thepassenger's head in an automobile crash regardless of the posture of thepassenger or the collision direction of an automotive vehicle.

Finally, as a distance adjustment unit, for adjusting a distance betweenthe first and second cushion units and the passenger's occipital bone,is constructed so as to be automatically turned on/off according to thepresence of the passenger without requiring a separate switchmanipulation, resulting in simplified control in operation of the firstand second cushion units.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A headrest for a vehicle comprising: a pair of support rods fitted atthe top of a backrest of an automotive vehicle seat; first and secondcushion units rotatably fitted at the top of the respective supportrods, respectively; at least one elastic member for elasticallyconnecting the first and second cushion units; jaw-restraint portionsformed at opposite sides of the first and second cushion units,respectively; and stoppers for keeping the support rods in animmobilized state after the first and second cushion units are rotatedto a predetermined degree.
 2. The headrest as set forth in claim 1,wherein the first and second cushion units include: a pair ofsymmetrical seating portions, respectively, formed at positionscorresponding to the passenger's occipital bone; and a pair of auxiliarycushion members located below the respective seating portions forsupporting the bottom of the occipital bone.
 3. The headrest as setforth in claim 1, wherein each of the stoppers includes: a case providedinside one of the first and second cushion units; a latch protruding atone end thereof out of the case so as to come into contact with theouter periphery of an associated one of the support rods; a springdisposed inside the case so as to elastically support the other end ofthe latch; a fixing groove defined at the outer periphery of the supportrod for allowing the latch to be lockably engaged therein as a result ofrotation of the corresponding cushion unit; and a pulling member forpulling out the latch inserted in the fixing groove.
 4. The headrest asset forth in claim 3, wherein the pulling member has: a wire connectedat one end thereof to the other end of the latch, the other end of thewire protruding out of the corresponding cushion unit; and a pull gripprovided at the outwardly-protruded end of the wire.
 5. A headrest for avehicle comprising: first and second cushion units rotatably fitted atthe top of a pair of support rods, respectively, the support rods beingfitted at the top of a backrest of an automotive vehicle seat, the firstand second cushion units having jaw-restraint portions formed atopposite sides thereof, respectively; impact sensors for detecting shockapplied to the vehicle in an automobile crash, and outputting signals;pressure sensors for detecting shock caused as the passenger's headcollides against the first and second cushion units, and outputtingsignals; a control unit for receiving the signals from the impact sensorand the pressure sensors, and outputting a control signal for causingrotation of the first and second cushion units; driving units forrotating the first and second cushion units according to the controlsignal; and stoppers for keeping the first and second cushion units inan immobilized state after they are rotated by a predetermined degree.6. The headrest as set forth in claim 5, wherein each of the stoppersincludes: a first detector positioned just inside the outer periphery ofone of the support rods; a second detector positioned just inside theinner periphery of a sleeve, which surrounds the support rod, so as tocorrespond to the first detector; and a locking member adapted tosupport the lateral surface of the support rod according to a signalgenerated when positions of the first and second detectors coincide witheach other as a result of rotation of the first and second cushionunits.
 7. The headrest as set forth in claim 5, wherein each of thedriving units includes: a servo-motor fixed inside one of the first andsecond cushion units, and adapted to be driven by the control signal;and a power-transmission member for transmitting a rotating force of theservo-motor to the support rod.
 8. A headrest for a vehicle comprising:first and second cushion units rotatably fitted at the top of a pair ofsupport rods, respectively, the support rods being fitted at the top ofa backrest of an automotive vehicle seat, the first and second cushionunits having jaw-restraint portions formed at opposite sides thereof,respectively; impact sensors for detecting shock applied to the vehiclein an automobile crash, and outputting signals; a distance adjustmentunit for maintaining a constant distance between the passenger's headand the first and second cushion units; a control unit for receiving thesignals from the impact sensor, and outputting a control signal forcausing pivotal rotation of the first and second cushion units; drivingunits for pivotably rotating the first and second cushion unitsaccording to the control signal; and stoppers for keeping the first andsecond cushion units in an immobilized state after they are pivotablyrotated by a predetermined degree.
 9. The headrest as set forth in claim8, wherein the distance adjustment unit includes: a distance sensor fordetecting a distance between the passenger's occipital bone and thefirst and second cushion units, and outputting a signal; the controlunit for detecting the signal from the distance sensor, and outputting acontrol signal if the detected distance exceeds a predetermined value,thereby allowing the first and second cushion units to be spaced apartfrom the passenger's head by a distance within a range of thepredetermined value; and a position adjustor for adjusting positions ofthe first and second cushion units according to the control signal fromthe control unit.
 10. The headrest as set forth in claim 8, wherein thevehicle comprises: a seat sensor for detecting the presence of thepassenger on the seat, and outputting a signal; and a switch for turningon/off a power source of the distance adjustment unit according to thesignal from the seat sensor.
 11. The headrest as set forth in claim 2,wherein each of the stoppers includes: a case provided inside one of thefirst and second cushion units; a latch protruding at one end thereofout of the case so as to come into contact with the outer periphery ofan associated one of the support rods; a spring disposed inside the caseso as to elastically support the other end of the latch; a fixing groovedefined at the outer periphery of the support rod for allowing the latchto be lockably engaged therein as a result of rotation of thecorresponding cushion unit; and a pulling member for pulling out thelatch inserted in the fixing groove.
 12. The headrest as set forth inclaim 6, wherein each of the driving units includes: a servo-motor fixedinside one of the first and second cushion units, and adapted to bedriven by the control signal; and a power-transmission member fortransmitting a rotating force of the servo-motor to the support rod. 13.The headrest as set forth in claim 9, wherein the vehicle comprises: aseat sensor for detecting the presence of the passenger on the seat, andoutputting a signal; and a switch for turning on/off a power source ofthe distance adjustment unit according to the signal from the seatsensor.